Drying kiln



March 11 1924. 1,486,743

E. HALLAM DRYING KILN Filed March 15, 1921 2 Sheets-Sheet 1 W/ TNES INVENTOR.

Patented Mar. 11, 1924.

tartan EDWIN A. HALLAM, OF PORTLAND, OREGON, ASSIG-NOB TO (MRS) MARY B. HALLAM, OF PORTLAND, OREGON.

DRYING KILN.

Application filed March 15, 1921.

To all whom it may concern:

Be it known that I, EDWIN A. HALLAM, a citizen of the United States, residing at Portland, in the county of Multnomah and State of Oregon, have invented new and useful Improvements in Drying Kilns, of which the following is a specification.

This invention relatesto improvements in drying kilns, and proposes a construction which is more especially applicable to the drying of lumber. It is a modification of the inventions forming the subjects-matter of my previous Patents No. 1,067,110 and No. 1,119,595, and is designed to provide a construction which improves the quality of the lumber and the process of drying it by quickening the drying period and more accurately controlling the circulation and dis tribution of moisture and air.

The object of my present invention is primarily to provide a closed circulation system,.of which the kiln chamber forms a part, the atmosphere of said chamber being withdrawn through one wall thereof and returned to such portion of said chamber and in such manner as shall best promote the even distribution of air to said lumber, according to the manner in which the latter is stacked, heat and humidity being supplied to the air within said chamber bydevices so arranged that cessation or irregularity in the heat or moisture supply, or non-uniformity in the rate of air flow will impart but a gradual change in the drying characteristics of the atmosphere within said chamber, whereby damage to the lumber, which would follow sudden changes of temperature or humidity, is avoided. 7

Another object of the invention is to provide means for gradually admitting a proportion of atmospheric air from a source extraneous to said circulation-system at such times as may be advantageous, for example when the air in the kiln chamber becomes saturated with aqueous vapor and no longer performs its drying function efficiently.

My prior patents show perforated pipes on the side walls or the ceiling of the kiln, or at both places, which direct the steam or gas coming through them to points where they will mix with the superheated air around the heater pipes, while according to Serial No. 452,609.

my present construction additional pipes are placed on the walls or ceiling, which additional pipes serve as conductors for the air or gas which is within the kiln and which is drawn out by an exhauster and then returned to the kiln and made to flow in any necessary direction to increase the circulation around or through the lumber.

I have foundthat perfect kiln drying of lumber is based on mainly three factors: 1st. The proper degree of heat applied to the lumber; 2nd. The proper amount of humidity in this heated air; and 3rd. The regular ity and evenness with which this air is circulated. According to my present invention these conditions are controlled and any accidental changes in the humidity and temperature occur slowly, rather than quickly. The advantages are obvious when it is remembered that dry kilns must run night and day and, at times, under three different managements during the twenty-four hours, and that the supply of steam may be shut off for a time at the boiler room for one cause or another. If the conditions in the drying chamber change slowly these temporary mistakes or mishaps do not alter conditions sufficiently to damage the lumber, and, where the change occurs slowly the trouble can be discovered in time and corrected. The elli' cient operation of kilns generally is greatly hampered by air currents of different temperatures and humidities circulating within a few feet of each other. In the construction forming the subject-matter of the present invention, Ihave arranged to forcibly admit the air at many parts of the room to break up these currentsand mix the air, thus bringing about an even condition throughout the room. It is not my purpose to cre ate a strong circulation but only to keep the air well mixed and continually moving in the right direction.

I am aware that there are other kilns wherein a power driven fan is employed to create circulation butin such kilns the fan either is adjacent the heater coils or draws and also to cause a change in the percentage of the humidity. This change may be caused by lower steam pressure at night than the reducing valve in the steam supply pipe is set for, with the result that the tan (generally operated by motor) delivers cold air to the lumber. When the pressure of the steam rises again the air is heated up and the humidity is greatly changed, thus damagin the lumber. The principal difference between my invention and other constructions is that, in the latter, where the fan draws the air through the coil it is necessary to handle nearly all the air contained inthe room in order to obtain sufiicient heat from the heater coil; whereas when the heater coil is in a compartment separate '1 from the lumber, the heat from the coil does not in any way assist the circulation but puts added work on the fan to draw the air through the coils.

According to my present invention the heater coil is within the kiln room where the lumber is to be dried, and this coil is neither connected to nor adjacent to the fan and the air conveyors of the latter, but is separate and independent. The advantages ofmy arrangement are: let. Should the fan be shut down for repairs or other causes, the room and lumber are not cooled but are still receiving heat from the heater coils: 2nd. The amount of air required to handled when the heater coil is separate from the fan and is located within the room is very much less because all the heat needed to heat the walls, air and lumber is afiorded by the coils within the room so that the fan does not handle thisheat at all, thus imposing upon the fan only the duty of causing a general stirring of the air. 3rd. Owing tothe independent arrangement of the coils and the fan, few of the accidents which are likely to occur to either one would bring about a harmful condition. of the humidity or temperature for several hours, whereas where the coil is attached to the fanor where the wall or pipe act as condensers the change is generally only a case of minutes. l

kiln embodying the features of my invention is illustrated in the accompanying drawings, wherein:

Figure 1, is a vertical longitudinal sectional view; liig. 2,'is a transverse sectional view of a single track kiln wherein the lumber is shown as pile d flat; Fig. 3 is a transverse sectional view of a single track kiln arrangement wherein the lumber is shown as piled on edge; Fig. 4, is a transverse sectional view of a single track kiln arrangement wherein the lumber is shown as stacked on edgebut ata rightangleto the e rf i e'c s- Similar charac e s of reference designate corresponding paa;.='. in all 'ot' the yiews.

The kiln room may be of any desired or approved construction in which the drying trucks 1 move on rails 2 supported by stringers 3. In the space between the rails, at a suitable distance below the trucks, there are arranged the usual radiators or heating coils 4. The lumber is stacked in any suitable manner on the trucks. Between the sides of the stack and the side walls of the kiln room are spaces 5 and 6 through which air may circulate around the trucks. The direction of air currents in these spaces is controlled by the air blow pipes 10, and the air intake pipes 11. These pipes 10 and 11 are placed at points adjacent the sides, root or floor of the room with a view to inducing the hot coil air the recirculated air to pass through the truck and mostly across the surfaces of the lumher. This is not intended to indicate that the pipe positions are adjustable but that their position is fixed according to the method "of piling the lumber practiced at the kiln. a

In the kiln shown in Figures 1 and 2, wherein the lumber is shown as stacked flat, 7 and 9 are steam jet pipes"arranged respectively on opposite sides and at the top of the kiln and communicating with source of steam, (not shown) and perforated on their under sides at 8, throughout their lengths or at suitable intervals for the admission of steam "to the kiln to supply the moisture necessary to prevent checking of the lumber. In this form of the invention the air pipes 10 are preferably arranged in pairs at opposite side walls of the kiln, the exhaust pipes 11 being uppermost and both the admission and exhaust pipes being connected to opposite ends of the blower 1a. The latter may be driven by any desired means but is here shown driven by a steam turbine 15 suppliedby means of a conduit 19 from the same source as are the steam pipes 7 and 9; The turbine 15 is provided with exhaust pipes 1? and 18, the former of which is connected with the steam pipe system of the kiln and the latter to the outside atmosphere, said exhaust pipes being controlled by the three-way valve 16. The air admission and exhaust pipes are provided with oppositely directed perforations 12 and 13 which respectively have the client of torcingthe air downwardly in the space between the side wall of the kiln d the stacked lumber and drawing the air downwardly from the upper part of said air space, thus creating a mild circulation which induces an upward drift of air through the pile of lumber, and its lateral diversion over the surfaces of the boards.

A small portion only of the body of air in the kiln chamber is directly affected by the heating coils 4, since the function of the admission and exhaust pipes 15 not to produce a decided directional current through the closed circulation system, which would pass the whole body of air into heat exchanging relationship with the coils 4tin a short time, but to gently stir the air in the kiln chamber so that the distribution of heat is by diffusion rather than by forced convectional flow from the heating coils. This makes it possible to tolerate abrupt fluctuations in the heat supply since corresponding sudden changes of temperature and humidity are not caused in the body of air in the kiln chamber.

The slide opening 22 permits a gradual change of the atmosphere within the kiln chamber when such becomes necessary.

Figures 3 and 4 illustrate slight modifications of the invention which are made necessary by different methods of stacking the lumber. In Figure 3 the lumber is shown as stacked on edge longitudinally of the edge and steam pipes, instead of being laid fiat as in Figures 1 and 2. In this case the air admission and steam pipes remain preferably on opposite side walls of the kiln but the air exhaust pipe is suspended from the ceiling thereof.

In Figure 5 the lumber is shown as stacked on edge transversely of the longitudinal disposition of the air pipes. In this case the exhaust pipes are preferably placed below the heating coils. The principle of the invention in both forms is the same in that the mild circulation between the air admission and exhaust pipes sets up a movement of air in the peripheral space between the stacked lumber and the walls of the kiln which induces a gradual drift of uniformly heated and humidified air through the spaces between the boards, the heating coils in both instances being out of the path of directional flow of air from the admission and the exhaust pipes.

While I have described what I have found to be very practical embodiments of my invention, it is nevertheless to be understood that my improved drying kiln may be exemplified in numerous other alternative constructions and I accordingly reserve the right of adopting all such legitimate changes as may be fairly embodied within the spirit andscope of the invention as claimed.

I claim 7 1. A drying kiln including walls forming a chamber, certain of said walls cooperating with material contained in said chamber to define a peripheral space within said chamber, and air inlet and exhaust pipes communicating with said chamber and connected to opposite sides of an air impeller to form with said chamber a closed circulation system, said inlet and exhaust pipes being provided with orifices opening into said peripheral space and arranged to avoid a directional flow from said orifices against the contents of said chamber but to induce a distributive drift of the relatively stagnant body of air in said chamber through interstitial spaces in the material contained therein.

2. A drying kiln including walls forming a chamber, certain of said walls cooperating with material contained in said chamber to define a peripheral space within said chamber, air inlet and exhaust pipes communicating with said chamber and connected to opposite sides of an air impeller to form with said chamber a closed circulation system, said inlet and exhaust pipes being provided with orifices opening into said peripheral space and arranged to avoid a directional flow from said orifices against the contents of said chamber but to induce a distributive drift of the relatively stagnant body of air in said chamber through interstitial spaces in the material contained therein, and means for humidifying the air in'said chamber.

3. A drying kiln including walls forming a chamber,'certain of said walls cooperating with material contained in said chamber to define a peripheral space within said chamber, air inlet and exhaust pipes communicating with said chamber and connected to opposite sides of an air impeller to form with said chamber a closed circulation system, said inlet and exhaust pipes being provided with orifices opening into said peripheral space and arranged to avoid a directional fiow from said orifices against the contents of said chamber but to induce a distributive drift of the relatively stagnant body of air in said chamber through interstitial spaces in the material contained therein, and steam admission pipes for humidifying the air in said chamber.

4. A drying kiln including walls forming a chamber, certain of said walls cooperating with material contained in said chamber to define a peripheral space within said chamber, air inlet and exhaust pipes communieating with said chamber and connected to opposite sides of an air impeller to form with said chamber a closed circulation system, said inlet and exhaust pipes being provided with orifices opening into said peripheral space and arranged to avoid a directional flow from said orifices against the contents of said chamber but to induce a distributive drift of the relatively stagnant body of air in said chamber through interstitial spaces in the material contained therein, and a heating coil out of the path of directional flow between said air admission and exhaust pipes.

5. A drying kiln including walls forming a chamber, certain of said walls cooperating with material contained in said chamber to define a peripheral space within said chamber, air inlet and exhaust pipes communicating with said chamber and connected to opposite sides of an air impeller to form with said chamber a closed circulation system, 'for admitting to said closed circulation sys- 10 said inlet and exhaust pipes being provided tem, air from an extraneoussource. with orifices opening into said peripheral In testimony whereof I have hereunto set space and arranged to avoid a directional my hand in presence of two subscribing Wit- I' flow from said orifices against the contents nesses.

of said chamber but to induce a distributive EDWIN A. HALLAM. drift of the relatively stagnant body of air Witnesses: in said chamber through interstitial spaces MILLARD SMITH,

in the material contained therein, and means N. L. SIMMONS. 

